Deep brain stimulation (DBS) has quickly emerged as an established therapy for the treatment of medically refractory movement disorders. However, current DBS techniques for electrode targeting and stimulation parameter selection do not account for the biophysics of neural stimulation. We are currently developing an integrated patient-specific modeling approach that will provide the clinician with realistic estimates of the volume of tissue activated during stimulation. There are a variety of fundamental assumptions that are made in these models, and the effects of these assumptions are unclear. The principal hypothesis of this study is that the 3D conductivity of the brain and the capacitance of the electrode-tissue interface each play a fundamental role in the neural response to DBS. We will evaluate the effects of these biophysical features with the aid of a 3D finite element model (FEM) that integrates detailed brain morphology, tissue conductivity and electrode properties with an innovative Fourier FEM solver. This system has the potential to improve patient outcomes by improving target and trajectory selection, reducing time in surgery, and maximizing stimulation benefit while minimizing side effects. [unreadable] [unreadable]